Jg12 vs JG8: specs compared
Updated 05 September 2026.
12 mm
Jg12 wins on tube outer diameter
On tube outer diameter, Jg12 leads: 12 mm versus 7.94 mm.
| Spec | Jg12 | JG8 |
|---|---|---|
| Designation | 12 mm OD | 5/16" (8 mm) OD |
| Size / thread | 12 mm OD tube | 5/16" (about 7.94 mm) |
| Fitting form | push-fit collet, metric | push-fit collet, imperial |
| Seals on | single O-ring plus a stainless collet grab-ring | single O-ring plus stainless collet grab-ring |
| Rating / role | John Guest Speedfit metric fittings for 12mm OD tube | John Guest Speedfit rated 16 bar at 1 C, 10 bar at 20 C |
| Tube OD | 12 mm | 7.94 mm |
Questions and answers
Which has the higher tube outer diameter, Jg12 or JG8?
On tube outer diameter, Jg12 leads: 12 mm versus 7.94 mm.
How do Jg12 and JG8 compare?
On tube outer diameter, Jg12 leads: 12 mm versus 7.94 mm.